Hot melt adhesives are used commercially for a wide variety of applications. The major advantage of hot melt adhesive systems is the lack of a carrier fluid which eliminates the need for drying the adhesive film once it is applied to the substrate. This elimination of the drying step overcomes hazards associated with solvent usage and also allows for faster production line speeds. Depending on the desired use, the degree of tack of the hot melt adhesives may be varied over a wide range to produce adhesives varying from pressure sensitive to non-pressure sensitive in character. Non-pressure sensitive are used, for example, in bookbinding, bag ending, case and carton sealing. Pressure sensitive hot melts are used in many applications, and particularly in disposables such as diapers, sanitary products and the like, where room temperature tack and long open time are required.
Hot melt adhesives have historically been based on petroleum derived polymers such as polyethylene, ethylene-vinyl acetate, styrenic block copolymers, and polypropylene to name a few. These compositions are further tackified, plasticized, and reinforced with a variety of resins, oils and waxes which are derived from both petroleum and naturally occurring feedstocks such as wood, gum and tall oil rosin and terpenes. These classic compositions suffer from the cyclical price cycles common to all oil derived materials, and also are generally very resistant to degradation once the articles employing them are disposed of.
The present invention stems from the growing movement away from petroleum derived raw materials to those derived from natural resources and as part of an effort to utilize raw materials which have demonstrated some level of degradation. The present invention utilizes a class of naturally occurring, thermoplastic, biodegradable copolymers derived from a non-petroleum feedstock as the base polymer. Such compositions advance the state of the art of hot melt adhesives by alleviating the dependence on petroleum based materials and by allowing for the development of hot melt adhesives which either degrade naturally after coming in contact with the soil or which can be composted.